The micropig is an excellent animal model for study of long-term blood pressure regulation because of (a) the similarity of its cardiovascular system to man, and (b) the fact that interactions with humans during experimentation pose fewer logistical problems than either primates, who may be aggressive, or dogs, who are naturally affiliative. A technology for study of long-term cardiovascular functions in the chronically instrumented and behaving micropig has been developed for study of interactions of stress and salt intake. The specific hypothesis under investigation is that behavioral stress which evokes respiratory suppression, bradycardia, and peripheral vasoconstriction also increases circulating concentrations of an endocrine factor which suppresses sodium pump activity. Confirmation of this hypothesis would provide a significant advance concerning the role of environmental and behavioral factors in long-term blood pressure regulation. Increased ability for nonpharmacological self-regulation of blood pressure could impact on a number of cardiovascular disorders of aging, including stroke.